FIXED OUTDOOR DEICING

70-377 B. Installation 426-10. General. Equipment for outdoor electric deicing and snow melting shall be identified as being suitable for: (1) The chemical, thermal, and physical environment, and (2) Installation in accordance with the manufacturer's drawings and instructions. 426-11. Use. Electrical heating equipment shall be installed in such a manner as to be afforded protection from physical damage. 426-12. Thermal Protection. External surfaces of outdoor electric deicing and snow-melting equipment that operate at temperatures exceeding 60°C (140°F) shall be physically guarded, isolated, or thermally insulated to protect against contact by personnel in the area. 426-13. Identification. The presence of outdoor electric deicing and snow-melting equipment shall be evident by the posting of appropriate caution signs or markings where clearly visible. 426-14. Special Permission. Fixed outdoor deicing and snow-melting equipment employing methods of construction or installation other than covered by this article shall be permitted only by special permission. C. Resistance Heating Elements 426-20. Embedded Deicing and Snow-Melting Equipment. (a) Watt Density. Panels or units shall not exceed 120 watts per square foot (0.093 sq m) of heated area. (b) Spacing. The spacing between adjacent cable runs is dependent upon the rating of the cable, and shall be not less than 1 inch (25.4 mm) on centers. (c) Cover. Units, panels, or cables shall be installed: (1) On a substantial asphalt or masonry base at least 2 inches (50.8 mm) thick and have at least 1½ inches (38 mm) of asphalt or masonry applied over the units, panels, or cables; or (2) They shall be permitted to be installed over other approved bases and embedded within 3½ inches (89 mm) of masonry or asphalt but not less than 1½ inches (38 mm) from the top surface; or (3) Equipment that has been specially investigated for other forms of installation shall be installed only in the manner for which it has been investigated. (d) Secured. Cables, units, and panels shall be secured in place by frames or spreaders or other approved means while the masonry or asphalt finish is applied. (e) Expansion and Contraction. Cables, units, and panels shall not be installed where they bridge expansion joints unless provision is made for expansion and contraction. 70-378 NATIONAL ELECTRICAL CODE 426-21. Exposed Deicing and Snow-Melting Equipment. (a) Secured. Heating element assemblies shall be secured to the surface being heated by approved means. (b) Overtemperature. Where the heating element is not in direct contact with the surface being heated, the design of the heater assembly shall be such that its temperature limitations shall not be exceeded. (c) Expansion and Contraction. Heating elements and assemblies shall not be installed where they bridge expansion joints unless provision is made for expansion and contraction. (d) Flexural Capability. Where installed on flexible structures, the heating elements and assemblies shall have a flexural capability compatible with the structure. 426-22. Installation of Nonheating Leads for Embedded Equipment. (a) Grounding Sheath or Braid. Nonheating leads having a grounding sheath or braid shall be permitted to be embedded in the masonry or asphalt in the same manner as the heating cable without additional physical protection. (b) Raceways. All but 1 to 6 inches (25.4 to 152 mm) of nonheating leads of Type TW and other approved types not having a grounding sheath shall be enclosed in a rigid conduit, electrical metallic tubing, intermediate metal conduit, or other raceways within asphalt or masonry; and the distance from the factory splice to raceway shall be not less than 1 inch (25.4 mm) or more than 6 inches (152 mm). (c) Bushings. Insulating bushings shall be used in the asphalt or masonry where leads enter conduit or tubing. (d) Expansion and Contraction. Leads shall be protected in expansion joints and where they emerge from masonry or asphalt by rigid conduit, electrical metallic tubing, intermediate metal conduit, other raceways, or other approved means. (e) Leads in Junction Boxes. Not less than 6 inches (152 mm) of free nonheating lead shall be within the junction box. 426-23. Installation of Nonheating Leads for Exposed Equipment. (a) Nonheating Leads. Power supply nonheating leads (cold leads) for resistance elements shall be suitable for the temperature encountered. Preassembled nonheating leads on approved heaters shall be permitted to be shortened if the markings specified in Section 426-25 are retained. Not less than 6 inches (152 mm) of nonheating leads shall be provided within the junction box. (b) Protection. Nonheating power supply leads shall be enclosed in a rigid conduit, intermediate metal conduit, electrical metallic tubing, or other approved means. 426-24. Electrical Connection. (a) Heating Element Connections. Electrical connections, other than factory connections of heating elements to nonheating elements embedded